Numerous machines have been developed specifically for comminuting empty glass containers. Breaking the containers up into fragments facilitates the recycling or disposal of the glass material. Machines developed for this purpose typically include an inlet opening through which the glass containers are inserted and an outlet opening through which the broken glass fragments and glass dust are ejected. To accomplish the breaking of the glass, these machines usually employ either a crushing apparatus or a hammermill type of breaker apparatus.
The problem with prior art machines that employ a crusher-type apparatus is their susceptibility to jamming when metal or paper is inadvertently dropped into the machine's inlet. To overcome this common occurrence the machines will either have the ability to crush the metal, or the machines will include an automatic dump apparatus that allows the machine to purge its contents when the anvil of the crushing mechanism meets an unusual resistance. Both of these solutions add an undesirable measure of complexity and expense to the device.
In machines that employ an internal breaker type apparatus, frequent and expensive maintenance is often required. These machines typically make use of a hammermill to break the glass. The hammermill is usually comprised of a number of rigid metal "hammers" that are mounted on the exterior surface of a central rotatable shaft. Each hammer must be sharp and straight for the machine to operate efficiently. However, during use the individual hammers rapidly become dulled. When metal objects are inadvertently fed into the device, the metal bends or breaks individual hammers thereby requiring their replacement.
One modification that has been used somewhat successfully in overcoming the failings of the prior art hammermills is the use of flexible hammers in lieu of rigid hammers. The flexible hammers are often in the form of movable chains that are attached to the machine's central shaft in a side-by-side orientation. The chains break the glass and allow any metal fragments or metal containers to rapidly pass through the device without causing any damage.
The known chain-type flexible hammermills, while providing a number of advantages over the prior art rigid hammermills, still suffer a number of failings. Firstly, the degree of comminution is uncontrolled, and as a result relatively large diameter fragments of glass are often ejected from the device's outlet. Since the outputted material includes these large glass fragments mixed with the smaller glass particles, the material cannot be easily recycled where it is mixed with asphalt or similar materials and used in road construction. Therefore, the large fragments must be separated from the smaller particles and removed from the product. Once done, the large fragments can be reentered into the machine and made smaller. While possible, this adds an unwanted additional step to the recycling process.
A second problem with prior art chain-type hammermills is that the layout of the device normally necessitates a gravity or blower induced flow of material through the device in order to prevent the material from clogging the unit. As a result, a large foundation is often required and when a blower is used, a significant increase in operating and maintenance costs is produced.
A third problem with prior art devices of this type is that the flowpath of the material within the machine is inefficient and uncontrolled. This results in high speed and only partially broken material being violently ejected from the device's outlet. This high speed material can be dangerous and can damage whatever container is being used to receive the broken glass.
Lastly, the present methods of fastening the chain type of hammer to the rotatable shaft make the chains difficult and time consuming to remove. Since the chains can become worn or broken during use, this presents a maintenance problem exacerbated by sharp glass particles and fragments that have become lodged against the retaining fasteners.